FIG. 1 is a block diagram of a prior art wavelength-division multiple access (“WDM”) passive optical network (“PON”) that uses injected light. The passive optical network has optical line terminals (“OLTs”) 103 and 114 within the central base station 100, optical lines 101 and 122 for transmission, remote nodes 102 and 123, and optical network (subscriber) units (“ONUs”) 111-113 and 124-126. For wavelength-division multiple access using injected light, the optical line terminals 103 and 114 have respective optical line terminals 103 and 114; optical transceivers 104-106 and 115-117; optical wavelength routers 107 and 118; broadband light sources 108, 110, 119, and 121; and broadband light source couplers 109 and 120.
Broadband light source couplers 109 and 120 supply the injected light. The broadband light source coupler 109 has 4-port optical elements and is described in South Korean Patent Application Number 2002-5326, filed Jan. 30, 2002, entitled Method and Apparatus for Decreasing and Compensating the Transmission Loss at a Wavelength-Division-Multiplexed Passive Optical Network and Apparatus Therfor. Broadband light source coupler 109 directs broadband light from the A-band broadband light source 108 to transmission line 101 to eventually be supplied to transmitters in the subscriber locations. Broadband light source (“BLS”) coupler 109 also directs the upstream signals of A-band broadband light from the transmission line 101 to the optical wavelength router 107. The broadband light source coupler 109 also directs broadband light from B-band broadband light source 110 to the optical wavelength router 107. Broadband light source coupler 109 transmits downstream signals of the wavelength-locked transceivers 104-106 from the optical wavelength router 107 to transmission line 101.
The A-band broadband light source 108 is used as an injected light of the optical transmitter of the optical subscriber, such as ONU 111. The B-band broadband light source 110 is used as an injected light of the optical transmitter within the optical line terminal. An injected light is injected into an optical transmitter.
A broadband light generated from the B-band broadband light source 110 is transmitted to the optical wavelength router 107 by the broadband light source coupler 109. The B-band broadband light is divided into wavelength segments by the optical wavelength router 107, and split wavelength segments of lights are used as injected light for optical transceivers 104-106.
The A-band and B-band designations are intended to be generic designations to cover different wavelength ranges, such as the C-band and L-band.
A Fabry-Perot laser diode, a semiconductor optical amplifier, or an optical modulator can be used as an optical transmitter in the optical transceiver. This transmitter modulates and amplifies the injected light to send optical signals. The principle of the A-band broadband light source 108 is similar to that of downstream signals.
The components of optical line terminal 114 operate in a similar manner to the components of optical line terminal 103.
Because a number of optical line terminals (e.g., OLT#1 through OLT#M) are positioned within central base station 100, the efficient configuration of the optical lines terminals (such as 103 and 114) is essential to reducing physical space, reducing cost, and reducing power consumption.
Prior art technology can be used for an optical network, and certain prior art technology is discussed in (1) an article by H. D. Kim, S. -G. Kang, and C. -H. Lee entitled A Low Cost WDM Source with an ASE Injected Fabry-Perot Semiconductor Laser, IEEE Photonics Technology Letters, Vol. 12, No. 8, pp. 1067-1069 (August 2000), (2) South Korean Patent Application No. 990059923, filed Dec. 21, 1999, which is publication number 20010063062 A, published Jul. 9, 2001, issued as South Korean Patent No. 325687, entitled Light Source For Wavelength Division Multiplexing (WDM) Optical Communication Using Fabry-Perot Laser Diode, and (3) U.S. patent application publication no. US 2003/0007207 A1, published Jan. 9, 2003 by Peter Healy et al. entitled Optical Signal Transmitter. For certain prior art optical networks, a number of optical networks are connected from one central base station. For certain prior art technology, the central base station independently requires a number of optical line terminals. A disadvantage of the prior art scheme of FIG. 1 is that the scheme requires much space and can be relatively costly.